Varying the power output of stirling cycle engines

ABSTRACT

Means provides the varying of mean pressure of the gaseous working medium in a multiple chamber reservoir at a higher temperature position in each engine cylinder connected to the lower temperature portion of the engine cylinder with valve regulating means governing the following of pressures of gas in the various stages and the cooler portion of the engine cylinder.

United States Patent 1 1 Hakansson Sept. 4, 1973 VARYING THE POWEROUTPUT 0F STIRLING CYCLE ENGINES [76] Inventor: Sven Anders SamuelHakansson,

Karolingatan 10, 212 34 Malmo, Sweden [22] Filed: Oct. 20, 1971 [21]Appl. No.: 191,038

[30] Foreign Application Priority Data Nov. 21, 1970 Great Britain55,470/70 [52] US. Cl. 60/241, 137/255 [51] Int. Cl F02g l/04, F02g H06[58] Field of Search 60/24 [56] References Cited UNITED STATES PATENTS7/1952 Rinia et a1. 60/24 2,607,190 8/1952 Kohler 60/24 2,794,315 6/1957Meijer 60/24 3,372,539 3/1958 Reinhoudt 60/24 3,496,720 2/1970 Neelen eta1 60/24 Primary ExaminerMartin P. Schwadron Assistant Examiner-Allen M.Ostrager Attorney-Laurence R. Brown [5 7 ABSTRACT Means provides thevarying of mean pressure of the gaseous working medium in a multiplechamber reservoir at a higher temperature position in each enginecylinder connected to the lower temperature portion of the enginecylinder with valve regulating means governing the following ofpressures of gas in the various stages and the cooler portion of theengine cylinder.

5 Claims, 10 Drawing Figures PATENTEBSEP 4am 3,756,018 sum 2 w 2 Fig. 4

INVENTOR. V S. HAKANSSON At'tow VARYING THE POWER OUTPUT F STIRLINGCYCLE ENGINES This invention relates to a device of the kind(hereinafter called the kind defined") used for varying the power outputof a Stirling cycle engine by varying the mean pressure of the gaseousworking medium, the said device comprising for each engine cylinder areservoir, connection means for connecting the reservoir to the coolerpart of the engine cylinder containing low temperature gaseous medium,and regulating means for governing the said connection means.

Known devices of the kind defined have the drawback that a continuousstepless variation between minimum and maximum output only can beobtained by choking the connection between the reservoir and therespective engine cylinder, and this involves a highly reduced degree ofefficiency when the engine is required to produce only a part of itsmaximum possible power output. However, devices of the kind definedallow very rapid changes in engine power output. They are also cheap inmanufacture and reliable in operation and are consequently desirable foruse in connection with Stirling cycle engines to be used in theautomotive industry.

The present invention is therefore intended to provide a device of thekind defined which will offer a higher degree of efficiency than thathitherto obtainable with the said known devices.

According to the present invention there is provided a device of thekind defined characterised in that the said connection means comprises anon-return valve always allowing the gaseous working medium in the wholereservoir to pass to the cooler part of the engine cylinder containinglowtemperature gas.

The invention is defined in the appended claims, and how it may beperformed is described in more detail with reference to the accompanyingdrawings, in which FIG. 1 is a diagrammatic view in axial sectionthrough a device according to the invention,

FIGS. 2 a, b, c and d show the positions of four valve members insections a-a, b-b, c-c, and d-d of FIG. I respectively the positions ofthe valves giving maximum load to the engine.

FIGS. 3 a, b, c and d show the same valves in their positionscorresponding to half load to the engine, and

FIG. 4 schematically shows some parts of a multicylinder Stirling cycleengine provided with a device according to the invention.

FIG. 1 shows a cylindrical housing 1 containing a cooler 2 and a space 3below the cooler 2, the said space 3 being connected to a compressionchamber (not shown in FIG. 1) by a channel 4.

A first wall 5 separates the space 3 from a first chamber 6. A secondwall 7 separates the chamber 6 from a second chamber 8, and a third wall9 separates the chamber 8 from a third chamber 10.

A valve tube 11 extends co-axially and centrally through the threechambers 6, 8 and 10, and fits tightly against tubular flanges l2, 13 onthe walls 7 and 9 respectively. At the top of the tube 11 a butterflyvalve member 14 is arranged to be axially movable and downwardlyactuated by a helical compression spring 15 which tends to establishcontact between the valve member 14 and the first wall 5 but allowsupward movements of the valve member 14 and passage of medium through anopening 16 in the wall 5 in case the pressure inside the chamber 6 ishigher than in the space 3. The butterfly valve member 14 is angularlylocked to the valve tube 11 which is movable in rotation about itslongitudinal axis by an arm 17 fastened to a solid extension 18 of thetube I1 passing through the bottom 19 of the cylinder 1.

Choke passages 20 and 21 are provided in the second wall 7 and the thirdwall 9 respectively.

In case the butterfly valve 14 is closed as shown in FIG. -2 a thepressure variations in the space 3 (which is connected to a compressionchamber via the channel 4) will allow gaseous working medium in thechamber 6 to pass into the space 3 during any period in which there is ahigher pressure in the chamber 6. Thus after a relatively short periodthe pressure in the first chamber 6 as well as the pressure in thesecond and third chambers 8 and 10 will correspond to the minimumpressure occurring in the space 3. This situation corresponds to maximumoutput of the Stirling cycle engine provided that no other outputdetermining factor is changed.

The valve tube 1 I and the flanges I2, 13 are provided with openings intheir respective axially overlapping sections, as will be seen mostclearly in FIGS. 2 and 3, sections b, c, and d. The interior of the tube1 l is always in connection with the first chamber 6 via openings 22. Asshown in FIG. 2 an opening 23 in the flange 12 is of angularly greaterextent than an opening 24 in the flange 13. The corresponding openings25 and 26 in the valve tube 11 are of equal size and are of the sameangular position. As viewed in section d an opening 27 in the valve tubeI 1 may communicate with a passage 28 in case the valve tube 11 isturned about 120 in the counter-clockwise direction from the positionshown in FIG. 2.

As shown in FIG. 3 an angular displacement of the tube 11 of about inthe counter-clockwise direction will cause a full opening of thebutterfly valve 14 and a nearly full overlapping of the openings 25, 23.

This will cause an easy communication between the space 3 and the firstand second chambers 6 and 8. The pressure variations in the chambers 6and 8 will thus follow the variations in pressure occurring in the space3. The pressure in the third chamber 10 will correspond to the meanvalue of the pressure in the chamber 8 because of the choke connection211.

Basically the operation of the device is as follows:

In case the butterfly valve 14 is closed maximum output and efficiencyis obtained. Minimum pressure prevails in all chambers 6, 8 and It).

In case the arm 17 is turned to rotate the tube 11 slightly thebutterfly valve 14 will open gradually. This will cause a rise inpressure in all chambers 6, 8 and 10 until the mean pressure of thespace 3 is obtained in all these chambers. This will cause a decrease inoutput, but also a decrease in efficiency. A further opening of thebutterfly valve 14 will allow a varying pressure in the chamber 6substantially completely following the pressure variations in the space3.

A further angular movement of the arm 17 to rotate the tube 11 in theopening direction will cause a full opening of the butterfly valve 14followed by a gradual opening of the connecion between the chambers 6and 8. The resistance offered by a partly opened connection to a furtherchamber will cause a decrease in efficiency, but the fully openedconnections offer a very slight resistance and thus a decrease in enginepower output can be achieved in combination with a minor decrease inefficiency.

FIG. 4 shows schematically and in vertical section the use of a deviceaccording to the invention as applied to a single-cylinder Stirlingengine.

The cylindrical housing 1 contains a cooler 2, and a heat-exchanger 30connected at its top to heater tubes 31 (only one of which is shown).The heater tubes 31 are connected to the top of the engine cylinder 32containing a displacer piston 33 and a working piston 34.

The passage 28 shown in FIG. 1 is also shown in FIG. 4 and leads to thespace below the working piston 34. Thus in case the arm 17 is turned torotate the tube 11 fully in the engine-throttling direction the spaceson both sides of the working piston 34 are short-circuited via the valvetube 1 l and will cause a complete stop of the engine.

In case of a multi-cylinder Stirling cycle engine a similarshort-circuiting will be obtained by connecting the passage 28 from theunit belonging to one cylinder to the corresponding passage 28 of theunit belonging to the following cylinder in the engine.

From the above description it will be readily appreciated that theillustrated device is of the kind defined and that the valve 14constitutes an adjustable valve which can be set to act as a non-returnvalve which always allows the working medium from the whole of thereservoir comprising the chamber 6, 8, and to pass to the cooler 2 andthrough the channel 4 to the cooler part of the engine cylinder 32.

What is claimed is:

l. in a Stirling cycle engine having a gaseous working medium and atleast one cylinder with a cooler part of the cylinder with a lowtemperature gaseous medium, a device for varying the power output byvarying the mean pressure of the gaseous working medium, the said devicecomprising for each engine cylinder a reservoir for containing saidgaseou working medium, gas flow connection means for connecting thereservoir to the cooler part of the engine cylinder containing lowtemperature gaseous medium, and regulating means for governing the saidconnection means comprising a nonreturn valve always allowing thegaseous working medium in the reservoir to pass to the cooler part ofthe engine cylinder containing low temperature gas wherein the reservoirconsists of a number of separate chambers connected in series, the firstchamber being connected to the said cooler part of the engine cylinderby said non-return valve, valve means connected to govern the flow ofthe gaseous medium between the said cooler part of the engine cylinderand the number of chambers including movable means being mechanicallycoupled to open connections successively to the series of chambers inthe order away from the cooler part of the engine cylinder and to shutoff the connections in the opposite order.

2. A device according to claim 1, in which the connection between thecooler part of the engine cylinder and the first chamber of thereservoir comprises a combination of a butterfly valve and a non-returnvalve.

3. A device according to claim 1, characterized in that a choke passageis present between each chamber of the reservoir.

4. A device according to claim 1 in a multi-cylinder engine,characterized in that the valves include means interconnecting all thereservoirs when the regulating means are moved to positions beyond thosecorresponding to the opening of the passages between all the chambers.

5. In a Stirling cycle engine having a-gaseous working medium, areservoir for receiving said medium and a cylinder compressing saidmedium, a device for varying the power output by varying the meanpresure of the gaseous working medium between said compression cylinderand said reservoir, comprising in combination, a single valve extendinginto said reservoir and having an element adjustable between a positionpreventing and a position permitting flow in both directions betweensaid cylinder and said reservoir and means on said valve operable insaid position preventing flow of said medium to prevent flow only in thedirection between said cylinder and said reservoir while permitting aflow of said medium in the direction from the reservoir to saidcompression cylinder.

* t I 2 k

1. In a Stirling cycle engine having a gaseous working medium and atleast one cylinder with a cooler part of the cylinder with a lowtemperature gaseous medium, a device for varying the power output byvarying the mean pressure of the gaseous working medium, the said devicecomprising for each engine cylinder a reservoir for containing saidgaseou working medium, gas flow connection means for connecting thereservoir to the cooler part of the engine cylinder containing lowtemperature gaseous medium, and regulating means for governing the saidconnection means comprising a non-return valve always allowing thegaseous working medium in the reservoir to pass to the cooler part ofthe engine cylinder containing low temperature gas wherein the reservoirconsists of a number of separate chambers connected in series, the firstchamber being connected to the said cooler part of the engine cylinderby said non-return valve, valve means connected to govern the flow ofthe gaseous medium between the said cooler part of the engine cylinderand the number of chambers including movable means being mechanicallycoupled to open connections successively to the series of chambers inthe order away from the cooler part of the engine cylinder and to shutoff the connections in the opposite order.
 2. A device according toclaim 1, in which the connection between the cooler part of the enginecylinder and the first chamber of the reservoir comprises a combinationof a butterfly valve and a non-return valve.
 3. A device according toclaim 1, characterized in that a choke passage is present between eachchamber of the reservoir.
 4. A device according to claim 1 in amulti-cylinder engine, characterized in that the valves include meansinterconnecting all the reservoirs when the regulating means are movedto positions beyond those corresponding to the opening of the passagesbetween all the chambers.
 5. In a Stirling cycle engine having a gaseousworking medium, a reservoir for receiving said medium and a cylindercompressing said medium, a device for varying the power output byvarying the mean presure of the gaseous working medium between saidcompression cylinder and said reservoir, comprising in combination, asingle valve extending into said reservoir and having an elementadjustable between a position preventing and a position permitting flowin both directions between said cylinder and said reservoir and means onsaid valve operable in said position preventing flow of said medium toprevent flow only in the direction between said cylinder and saidreservoir while permitting a flow of said medium in the direction fromthe reservoir to said compression cylindEr.